The present invention relates to a vibration absorbing hose, more specifically to a vibration absorbing hose which is excellent in pressure resistance and gas permeation resistance, and suitable for plumbing in an engine room for a motor vehicle.
In the past, a tubular rubber hose mainly composed of rubber elastic material has been widely used in a variety of plumbing or piping means for industrial and automotive applications. As such rubber hose has excellent vibration absorbing property, it is often arranged in vibration regions for the purpose of restraining vibration transmission.
For example, in case of plumbing hose such as hose for fuel system or refrigerant conveying hose (air conditioner hose) used in an engine room of a motor vehicle, the plumbing hose serves as to absorb engine vibration, compressor vibration of an air conditioner and other various vibration generated during car driving, and to restrain transmission of the vibration from one member to the other member which are joined via the plumbing hose.
Meanwhile, regardless of industrial or automotive applications, hoses for oil system, fuel system, water system and refrigerant system are formed in multi-layered construction including inner rubber layer, outer rubber layer and reinforcement layer interposed between the inner and outer rubber layers, for example, as disclosed in the Patent Document 1 below. The reinforcement layer is typically constructed by arranging or braiding reinforcing yarns.
FIG. 12 shows construction of a refrigerant conveying hose (air conditioner hose) which is disclosed in the Patent Document 1. The refrigerant conveying hose has multi-layered construction. Reference numeral 200 in FIG. 12 indicates tubular inner rubber layer. Resin inner layer 202 is formed or laminated in an inner side of the inner rubber layer 200. And, first reinforcement layer 204 is formed or laminated on an outer side of the inner rubber layer 200, and second reinforcement layer 206 is formed or laminated on an outer side of the first reinforcement layer 204 with intervening intermediate rubber layer 208 between the first and the second reinforcement layers 204, 206. The first reinforcement layer 204 is formed by winding reinforcing yarn or yarns spirally while the second reinforcement layer 206 is formed by winding reinforcing yarn or yarns spirally in the reverse direction to the winding direction of the first reinforcement layer 204. Further, outer rubber layer 210 is formed or laminated on outer side of the second reinforcement layer 206 as outermost layer which serves as cover layer.
In this example, the reinforcement layers 204, 206 are formed by arranging or winding reinforcing yarns spirally. On the other hand, such reinforcement layer is also likewise formed by braiding or braid-weaving reinforcing yarns. FIG. 13 shows an example of a hose having such braided reinforcement layer. Reference numeral 212 in FIG. 13 indicates reinforcement layer which is formed by braiding reinforcing yarns between the inner rubber layer 200 and the outer rubber layer 210. In this example, resin inner layer 202 is also formed in an inner side of the inner rubber layer 200.
As noted from these examples, all of conventional hoses which have been provided including reinforcement layer therein are shaped straight-sided or straight-walled tube having inner and outer side surfaces which are straight in a longitudinal direction. Meanwhile, in case of such straight-sided tubular hose, the hose needs to be designed to have a length according to rigidity of the hose in order to ensure favorable vibration absorbing property.
In particular, compared to low-pressure hoses for fuel system, water system or the like, a longer length is required for high pressure hoses such as those for oil system (for example, power steering system) or refrigerant system (refrigerant conveying system) to ensure sufficient vibration absorbing property and reduce transmission of noise and vibration to vehicle interior, with corresponding increases in rigidity of the hoses. For example, in case of refrigerant conveying hose, typically the hose of 300 mm to 600 mm in length is adapted to secure vibration absorbing property and reduce transmission of noise and vibration, even for plumbing or piping for direct distance of 200 mm.
However, an engine room is crammed with variety of components and parts. And, specifically in these days, due to necessity to ensure a compartment space as large as possible, an engine room has been designed in compact size and space or clearance in the engine room has been more and more narrowed. Therefore, under the circumstances, if a long hose is arranged in the engine room, it bothers an design engineer to design plumbing arrangement to avoid interference with other components or parts and an operator to handle the hose when arranging the hose in the engine room. Further, such plumbing design and handling of the hose according to types of a motor vehicle should be devised. These result in excessive work load in mounting and assembling vehicle parts and components.
In view of foregoing aspects, it is demanded to develop a rubber hose (rubber-elastic-material hose) of which properties such as vibration absorbing property are improved. One of the means to design the hose in short length without loosing favorable vibration absorbing property is to form the hose with corrugations. Actually, the following Patent Document 2 discloses a fuel hose (a hose for fuel system) of motor vehicle which is provided with corrugations.
FIG. 14 is a view to explain the fuel hose disclosed in the Patent Document 2. In FIG. 14, reference numeral 214 indicates tubular rubber layer, and reference numeral 216 indicates resin inner layer which is formed in the inner surface of the rubber layer 214. As shown in FIG. 14, the fuel hose is provided with corrugated portion 218. Therefore, in this fuel hose, it is possible to effectively absorb generated vibration thanks to flexibility of the corrugated portion 218 in spite of short length of the fuel hose.
Meanwhile, just by providing the hose with corrugated portion 218 as shown in FIG. 14, flexibility can be obtained, but sufficient pressure resistance cannot be ensured. That is, the hose of the disclosure is called a filler hose, and is adapted to a fuel filler opening. Therefore, pressure resistance is not specifically required for the hose of the disclosure. The construction of the hose shown in FIG. 14, wherein bursting pressure is under 1 MPa, may be adapted to a low-pressure hose such as filler hose, but may not be adapted without modification to a hose for which high-pressure resistance is required.
One of means to provide a hose including such corrugated portion or corrugations with pressure resistance may be to form on the hose a reinforcement layer which has a considerable reinforcing effect. The reinforcement layer should not diminish flexibility which the corrugations inherently have, and should be easily and favorably formed on an outer surface side of the rubber layer.
Further, in case that a vibration absorbing hose is applied as air conditioner hose for conveying refrigerant or the like, for example, in an engine room of a motor vehicle, the hose is required to have gas permeation resistance, namely, impermeability to gas from the inside to the outside of the hose, and impermeability to water from the outside to the inside thereof as well as pressure resistance and vibration absorbing property. In such a case, the hose should be provided with gas permeation resistance, in addition to pressure resistance and vibration absorbing property. However, in the hose having a corrugated portion, a surface area is increased in the corrugated portion. So, it is disadvantageous to gas permeation resistance, and countermeasures are required accordingly.
Patent Document 1JP, A, 7-68659Patent Document 2U.S. Pat. No. 6,279,615
Under the circumstances described above, it is an object of the present invention to provide a novel vibration absorbing hose which has excellent pressure resistance and gas permeation resistance, and does not loose sufficient vibration absorbing property if formed short in length.